“Old mascara can definitely give you an infection—the moistness and tube is a breeding ground for germs,” board-certified dermatologist Mona Gohara, M.D., previously shared with mbg. (Especially given the fact that you dip the wand in and out, increasing the chance of contamination.) That bacteria can contribute to dermatitis, which is particularly prevalent around the eyes since the skin is thinner. As a general rule of thumb, many experts recommend tossing your mascara every two months, just to be safe.

While you may hear of old tricks and tips to extend the shelf life of your trusty tube (example: Add eye drops to your mascara to re-moisten the formula), these hacks are a major no. “If a product is old and crusty and you add something to it, the amount of bacteria you could be creating is frightening,” says celebrity esthetician Joanna Vargas about how to make beauty products last longer. If it’s dried up, there’s a reason, and reviving it can do way more harm than good.

https://www.mindbodygreen.com/articles/lash-mistakes-experts-see-all-the-time